A locomotive is a complex system with numerous subsystems, each subsystem interdependent on other subsystems. An operator aboard a locomotive applies tractive and braking effort to control the speed of the locomotive and its load of railcars to assure safe and timely arrival at the desired destination. To perform this function and comply with prescribed operating speeds that may vary with the train's location on the track, the operator generally must have extensive experience operating the locomotive over the specified terrain with various railcar consists, i.e., different types and number of railcars.
However, even with sufficient knowledge and experience to assure safe operation, the operator generally cannot operate the locomotive to minimize fuel consumption (or other operating characteristics, e.g., emissions, wheel wear, track wear) during a trip. Multiple operating factors affect these variables, including, for example, emission limits, locomotive fuel/emissions characteristics, size and loading of railcars, track frictional forces, distribution of wheel-on-rail forces throughout the train, weather, traffic conditions, and locomotive operating parameters (which here refers to controllable elements of train operation, such as a notch number or brake applications). An operator can more effectively and efficiently operate a train (through the application of tractive and braking efforts) if provided with control information that optimizes performance during a trip while meeting a required schedule (arrival time) and using a minimal amount of fuel or optimizing another performance component such as wheel or track wear, despite the many variables that affect performance. Thus it is desired for the operator to operate the train under the guidance (or control) of a system, method or computer software code that advises the application of tractive and braking efforts to optimize one or more performance components or trip/mission objectives.
Train wheels are subject to normal wear due to friction contact between the wheel and the rail. To reduce wheel and flange wear on curves it is known to lubricate the wheel flanges prior to traversing the track curve. Notwithstanding the lubrication, the wheels tend to wear. The wheel rim width and flange width decrease while the flange height increases. It is necessary to periodically measure the rim width, the flange width and the flange height to ensure that the wheels have not worn to the point of unsafe train operation. Wheels can be recut (referred to as wheel truing) to restore the wheel profile if wheel wear causes the profile to exceed permissible tolerances related to rim width, flange width and flange height.
Measuring these wheel dimensions is difficult as the wheels are surrounded by other locomotive parts. Thus there is limited space and difficult access to the pertinent wheel features, especially the flange, which is on the inner surface of the wheel. Also, the measurements are made in poor ambient conditions, such as dim light.
Control of train speed through track curves can reduce wheel and track wear, requiring less frequent measurement of wheel dimensions and track conditions, without sacrificing train safety and comfort for train passengers. It is well known that maximum allowable forces on a curved track section can be translated to upper limits on forward speed of a locomotive, a locomotive consist and train railcars, such as freight railcars. The lateral-to-vertical force ratio (L/V) can be calculated to determine safe speeds with a low likelihood of derailment. Depending on the super-elevation of the track (lateral “tilt” toward/away from the center of curvature), there may also be a minimum speed of traversal to assure an acceptable L/V ratio.
The current technology in locomotive traction control is based on an average North American curve of approximately 2.5 degrees. In addition to reducing wear, if real-time rail data, including current track curvature and track super-elevation, is provided, the locomotive traction system can be optimized for current track conditions resulting in better train efficiency.
Track conditions can also can also have a detrimental effect on track wear. Conditions such as track warping and humping may occur. Relative and repetitive motion between the track/ties and the roadbed (e.g., ballast) due to the train loads can also, over time, cause the track rails to wear. Both wheel wear and track wear increase the likelihood of a train derailment.
Controlling train operation to limit track and wheel wear improves train safety and extends the time between wheel and rail maintenance actions.